Graphic arts products such as lithographic films consist generally of a photographic silver halide emulsion in a hardened organic colloid binder coated on a suitable support, and serve for the production of half-tone dot images useful in letterpress printing, lithography and the like.
The silver halide emulsions commonly used in the graphic arts field, for example, silver bromochloride, are expensive mainly because of their silver content. The industry is constantly considering ways to reduce the amount of silver halide used. Unfortunately, under ordinary conditions, reduction of silver coating weight for the standard single layer emulsion structure decreases speed, reduces top density, and, in the case of lithographic films, degrades dot quality. One means of better utilizing silver to increase the efficiency of litho systems is to remove or decrease the adjuvant normally added to improve dot quality (the "dot adjuvant"), which increases the speed substantially. However, in the absence of the dot adjuvant, dot quality is unacceptable, aging stability is poor, and overdevelopment fog result. Conventionally, polyoxyethylene compounds are used as dot adjuvants, for example.
The main object of the present invention is to reduce the silver content of a lithographic film and at the same time increase its speed, without the disadvantages described above.